It is recognized in digital communications that a precise knowledge of the parameters characterizing the quality of a communications channel is extremely important for efficient data transmission. This is related to the classical Shannon result stating that the data rate of a communications channel is a function of the signal-to-noise ratio (SNR). For a given signal, the increase in the noise level affects the quality of transmission adversely. The amount of information that can be reliably transmitted over a communications channel decreases as the noise increases.
The precise knowledge of the SNR of a channel dictates how much information will be ultimately transmitted. If one underestimates the SNR, the channel efficiency drops compared to the most efficient transmission mode. If one overestimates the SNR then more data is transmitted but the information is unreliable. Therefore, it is extremely important to be able to estimate the SNR of a communications channel in a precise and timely manner.
This is even more important in modern wireless communications that meet new challenges with respect to increasingly complex propagation environments. Typical examples of such environments would be urban areas, office buildings, military vessels, war zones, jungles, rock concerts etc. Some of these environments are characterized by severe multipath effects, others by strong fading, and others by both. When a communication session between two stations is initiated in such an environment, the SNR should be measured on both ends of the channel as precisely as possible and further communications over this channel are stipulated by the SNR value measured.
The present application is related to U.S. Patent Disclosure No. 547174, titled “Method and Apparatus for Determining the Quality of a Communications Channel in Complex Propagation Environments”, invented by Vlad Mitlin, filed on Feb. 18, 2004, and owned by the same assignee now and at the time of the invention.